53’70
COMMUKICATIONS TO THE EDITOR
Acknowledgments.-The authors thank Miss P. A. Carney, R . 11. Murch, and F. A. Kramer for assistance in determining n.m.r. spectra, and the Air Force Office of Scientific Research for financial support. DEPARTMENT O F CHEMISTRY UNIVERSITY OF \$’ISCONSIS MADISON, \VISCOSSIX
ROBERTE. BAILEY ROBERTVEST
VOl. 86
molecular proton transfers which lend substantial support to these “conducted tour’’mechanisms. Compound 111,5when treated with various bases in a variety of deuterated solvents, gave IV6 with intramolecularity t h a t varied from 17 to 98y0 (Table
RECEIVED SEPTEMBER 12, 1964
Base-Catalyzed Intramolecular 1,3- and 1,5-Proton Transfers
Sir:
I
COZCHS
COzCHs
Since the report of the first base-catalyzed intramolecular 1,3-proton transfer, enough other examples2 have appeared in the literature to suggest that the phenomena might be rather general. Support for this view is found in a number of examples of enzymecatalyzed intramolecular proton transfers t h a t have been observed.
IV (IV-d)
I11
TABLE I INTRAMOLECULARITY Run no.
IN
BASE-CATALYZED P R O T O N (DEUTERON) TRANSFERS I N TRIENE111 TO GIVE TRIARYLMETHANE Iv AND DEUTERATED ACETYLENE ( V ) TO GIVE ALLENEVIa
Compd.
Solventh
Base
I11 I11 I11 I11 111 111 111 111
T,
O C .
70
IN
intramolecular
(CHZOD)~ DOCHzCHzOK 55 17 (CHz)dO-lO% Dz0 DOSa 25 34 (CDa)zSO-lO:? CH30D CHaOK 25 40 CHaOD CH30Sa 25 47 5 t-BuOD t-BuOK 25 50 75 98 6 (C2Hj)rCOD (C3H7)3N -I 97 ( C2Hj)3CODC ID (C3Hi)3x 8 ( C2H5)3CODd 98 (C3HihX ID 9 1t-BuOD t-BuOK 30 22 i 3 10 V-d* CHjOH CHjOK 30 19 11 V-de (CH3)zSO-1 .6M t-BuOH N( CHpCHz)3S 30 88 12 T‘-de (CHa)zSO-3.9 CHaOH N( CHzCHz)3N 30 88 13 V-de (CHa)zSO-3 9 M CH30H’ K( CHzCH2)jN 30 85 14 V-de (CH$),SO-3 9 X CHjOH’ (CH2)jSH 30 58 a .I11 deuterium analyses were made by combustion and falling drop method ( J . S e m e t h ) . Products once formed underwent little if any exchange under conditions of their formation. r, Solvents 97-100Tc deuterated where deuterium is indicated. Solution was Solution was 0.1 -26 in (CzH7)3NDI. e 95% of 1 atom of deuterium. Results were corrected accordingly. 0.1 JI in (C4Hy)aSI. f Solution was 0.14 Jf in S(CH2CHz)zKHI. 1 2 3 4
rr-
A l I
I n studies of the stereochemistry of base-catalyzed hydrogen-deuterium exchange of I and 11, examples of intramolecular racemization (isoracemization) were interpreted as occurring by a series of intramolecular proton transfers (conducted tour mechanism). Some of the steps involved 1,6-proton transfers across an aromatic system ( I ) , others 1,3-proton transfers from carbon (Y to a cyano group to nitrogen and back to
I
I1
carbon. 11-e have now observed examples of intra(1) L). J C r a m and I< T. Uyeda, J . A m . C h e m . S O C .84, , 4358 (1962). ( 2 ) ( a ) S . B a n k , C A Rowe, J r . , and A . Schriesheim, i b i d . , 86, 2115 ( 1 9 6 3 j , ( b j K . B . Bates. R. H . Carnighan, a n d C . E. Staples, i b i d . , 86, 3032 (196B), ( c j 1%‘. von E . Iloering a n d P. P. Gaspar, ibid., 86, 3043 (1963); ( d ) G. Bergsen and A . 51. lveidler, A c i a C ‘ h e m Scand.. 17, 862, 1798 (1963j, (e) G . Bergsen. t b z d . . 17, 2691 (1963j, ( f ) I > . J. C r a m a n d It. T . Uyeda. .I A m / h e ? n . Sor , in p i - ~ s s (~31 (a) F. S K a w a h a r a a n d P Talalay. J . Bioi. (‘hem.. 2 3 6 , P C I (1960j, f b i B. V.‘ i l g r a n o f f . H Eggerer, U Henning. a n d F . Lynen. i b t d . , 236, 326 (19601. (cl H. C Killing and hl. J. Coon, ibid . 236, 3087 (1960). 1 4 1 I ) . J . C r a m and I. Gosser. J . A m ( h e w , S o r . 86, 2950 (1964j.
I). This rearrangement involves proton transfer across the face of a benzene ring. Compound V (deuterated) under similar conditions with base in protonated solvents gave VI with intramolecularity that varied between about 20 and 887G (Table I ) The isomerization of triene I11 to aryl compound IV can be visualized as occurring by one 1,5-rearrangement, or by two successive 1,3-rearrangement.s. Evidence t h a t the latter type of mechanism makes little, if any, contribution is shown by the fact t h a t no deuterium could be detected in the aromatic rings of IV (combination of n.m.r. and combustion techniques) produced in those runs which gave low intramolecularity (1-5). Had intermediates such as VII-d intervened, some deuterium should have been incorporated into the ortho position of the para-substituted ring of IV. These rearrangements are interpreted as occurring largely through ion-pair intermediates whose carbanion is hydrogen bonded to the molecule of oxygen or nitrogen acid generated by proton (deuterium) abstrac( 5 ) R . Heck, P. S. Magee, a n d S. Winstein, r e i v a h e i f v o i i L e l i e r s , 3 0 , 2033 (1964). ( 6 ) All nem compounds used in this investigation gave carbon and hydrogen analysis within 0.37c of theory. All old compounds gave physical properties which corresponded t o literature values.
5371
BOOKREVIEWS
Dec. 5, 1964
tion by base. Although the carbanion might be hydrogen bonded by external deuteron (proton) donors in the medium, deuteron (proton) capture a t sites distant from the cation of the ion pair would generate dissociated ions. Such a process is favorable only in solvents of high dielectric constant. Recapture by a new site of the proton (deuteron) originally abstracted to form the carbanion produces an ion pair when metal alkoxides serve as bases, and a neutral molecule when amines are used. The intramolecular rearrangements of I11 to IV and of V to VI probably occur by migration of protons
(deuterons) as conjugate acids of the catalyst across the face of a a-cloud of electrons containing a negative charge. Migration from the front face of the a-cloud to the rear face by the migrating group would involve breakage of the hydrogen bond and a t least partial dissociation of the ion pair, and is an unlikely process in those solvents which exhibit high intramolecularity. Therefore, these results imply t h a t if suitable optically active analogs of I11 and V were submitted to conditions that gave high intramolecularity, the products would be of high optical purity. Thus asymmetric induction over several bond lengths is anticipated. The stereochemical experiments of Bergsen and Weidler2d,e and of Jacobs and Dankner’ give force to this expectation, which is currently being tested. ( 7 ) T.L. Jacobs and D. Dankner, J. Org. Chem., 2 2 , 1424 (1957).
DONALD J. CRAM CONTRIBUTION No. 1760 DEPARTMEXT O F CHEMISTRY F . WILLEY UXIVERSITY OF CALIFORNIA AT Los ANCELES H . P. FISCHER DONALDA. S.COTT Los ANGELES,CALIFORNIA RECEIVEDSEPTEMBER 28, 1964
BOOK REVIEWS Divalent Carbon. By J. HINE, Professor of Chemistry, Georgia Institute of Technology. The Ronald Press Co., 15 East 26th St., New York 10, N. Y . 1964. vii 206 pp. 15 X 21 cm. Price, $7.00.
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Considering the volume of published material on the chemistry of methylenes, i t is amazing t h a t the publication of the first comprehensive and acceptable review in English appeared only after this field has enjoyed a n immense popularity for more than a’decade. It is fortunate t h a t the first book entirely devoted to methylenes has been written by an author who has revitalized the interest in divalent carbon compounds through his pioneering studies on the mechanisms of haloform hydrolyses. The book consists of eight chapters which proceed from a discussion of the physical and physical-organic chemistry of methylene itself to a treatment of the chemistry of a variety of methylene derivatives. Included in the latter are dihalomethylenes, alkoxy-, alkylthio-, and monohalomethylenes, double-bonded derivatives of divalent carbon, and miscellaneous other substituted methylenes. The last three chapters present a discussion of mechanisms of a-eliminations, of pyrolytic and photolytic decompositions of diazo compounds, and of a number of other reactions which may proceed through the intermediacy of divalent carbon species. The 218 references are taken from the literature available to the author t o mid-1962. This includes some material with publication dates of 1963. Throughout the book, Hine has avoided the term “carbene”; instead he seems to prefer the Chemical Abstracts system which names all divalent carbon compounds as derivatives of methylene. I n the authors own words, the emphasis of the book is on “mechanisms of reactions involving methylenes and the effect of structure on reactivity in these reactions.” As a consequence of this guideline, many references of interest mainly to the synthetic chemist are dealt with rather briefly, or are omitted entirely. Undoubtedly other books on divalent carbon will be published soon, and since it is likely t h a t synthetic aspects d l be stressed in one or the other, this restriction cannot be considered a shortcoming. The real strength of this monograph lies in its attempt to develop a general and consistent framework into which the vast volume of experimental data may be fitted. In the discussion Hine does not shy away from giving his own interpretations of many experimental observations even if his conclusions are not the same as those of the original authors. Another enjoyable aspect is the large number of suggestions of experiments which should be done to solve remaining problems. Considering
the size of the book, most aspects of mechanistic methylene chemistry in solution have been covered adequately. .4 somewhat more detailed description of the vapor phase work might have added to the value of the book. The only severe criticism must be directed towards the publisher. A production time of 18 months cannot be tolerated when the subject of the monograph is in a state of dynamic development. As a result of this time lag, the most exciting recent developments in methylene chemistry, such as the information on ground-state properties of divalent carbon compounds obtainable from e.s.r. studies, are only mentioned in a few words. In conclusion, Hine succeeded in writing a very useful and stimulating book. Acquisition can be highly recommended to any one interested in organic reaction mechanisms. It should be included in the reading list for organic graduate students. They will profit not only from being familiuized with divalent carbon chemistry, but, more important, they will be given an excellent view on the methods and techniques used to study short-lived reactive intermediates in general. DEPARTMENT OF CHEMISTRY THEUNIVERSITY OF CHICAGO CHICAGO 37, ILLINOIS
GERHARD L. CLOSS
Electronic Spectra and Quantum Chemistry. By C. SASDORFY, Professor of Chemistry, University of Montreal. PrenticeHall, Inc., Englewood Cliffs, S . J . 1964. xiii 385 pp. 16 X 23 cm. Price, 814.95.
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This book was originally published in French in 1959 as “Les Spectres Electroriiques en Chimie Theorique,” and its German translation ( 1961) was previously reviewed in this journal ( J . A m . Chem. Soc., 81, 2656 (1962)). The present volume, as the author remarks in his preface, is a greatly augmented version of these previous editions. After a short introduction on units, and a somewhat longer one on the basis of the variation and perturbation methods in quantum mechanics, there is a short chapter on energy calculations by the Huckel MO method, and another considerably longer one on the corresponding valence bond technique using “structures.” The emphasis is on the presentation of complete detail of each treatment, so that not even the smallest arithmetic steps are passed over.
